/*
 * File imported from FreeBSD, original by Poul-Henning Kamp.
 *
 * $FreeBSD: src/lib/libcrypt/crypt-md5.c,v 1.5 1999/12/17 20:21:45 peter Exp $
 *
 * contrib/pgcrypto/crypt-md5.c
 */

#include "postgres.h"

#include "px.h"
#include "px-crypt.h"

#define MD5_SIZE 16

static const char _crypt_a64[] =
"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

static void
_crypt_to64(char *s, unsigned long v, int n)
{
    while (--n >= 0)
    {
        *s++ = _crypt_a64[v & 0x3f];
        v >>= 6;
    }
}

/*
 * UNIX password
 */

char *
px_crypt_md5(const char *pw, const char *salt, char *passwd, unsigned dstlen)
{
    static char *magic = "$1$"; /* This string is magic for this algorithm.
                                 * Having it this way, we can get better later
                                 * on */
    static char *p;
    static const char *sp,
               *ep;
    unsigned char final[MD5_SIZE];
    int            sl,
                pl,
                i;
    PX_MD       *ctx,
               *ctx1;
    int            err;
    unsigned long l;

    if (!passwd || dstlen < 120)
        return NULL;

    /* Refine the Salt first */
    sp = salt;

    /* If it starts with the magic string, then skip that */
    if (strncmp(sp, magic, strlen(magic)) == 0)
        sp += strlen(magic);

    /* It stops at the first '$', max 8 chars */
    for (ep = sp; *ep && *ep != '$' && ep < (sp + 8); ep++)
        continue;

    /* get the length of the true salt */
    sl = ep - sp;

    /* */
    err = px_find_digest("md5", &ctx);
    if (err)
        return NULL;
    err = px_find_digest("md5", &ctx1);

    /* The password first, since that is what is most unknown */
    px_md_update(ctx, (const uint8 *) pw, strlen(pw));

    /* Then our magic string */
    px_md_update(ctx, (uint8 *) magic, strlen(magic));

    /* Then the raw salt */
    px_md_update(ctx, (const uint8 *) sp, sl);

    /* Then just as many characters of the MD5(pw,salt,pw) */
    px_md_update(ctx1, (const uint8 *) pw, strlen(pw));
    px_md_update(ctx1, (const uint8 *) sp, sl);
    px_md_update(ctx1, (const uint8 *) pw, strlen(pw));
    px_md_finish(ctx1, final);
    for (pl = strlen(pw); pl > 0; pl -= MD5_SIZE)
        px_md_update(ctx, final, pl > MD5_SIZE ? MD5_SIZE : pl);

    /* Don't leave anything around in vm they could use. */
    px_memset(final, 0, sizeof final);

    /* Then something really weird... */
    for (i = strlen(pw); i; i >>= 1)
        if (i & 1)
            px_md_update(ctx, final, 1);
        else
            px_md_update(ctx, (const uint8 *) pw, 1);

    /* Now make the output string */
    strcpy(passwd, magic);
    strncat(passwd, sp, sl);
    strcat(passwd, "$");

    px_md_finish(ctx, final);

    /*
     * and now, just to make sure things don't run too fast On a 60 Mhz
     * Pentium this takes 34 msec, so you would need 30 seconds to build a
     * 1000 entry dictionary...
     */
    for (i = 0; i < 1000; i++)
    {
        px_md_reset(ctx1);
        if (i & 1)
            px_md_update(ctx1, (const uint8 *) pw, strlen(pw));
        else
            px_md_update(ctx1, final, MD5_SIZE);

        if (i % 3)
            px_md_update(ctx1, (const uint8 *) sp, sl);

        if (i % 7)
            px_md_update(ctx1, (const uint8 *) pw, strlen(pw));

        if (i & 1)
            px_md_update(ctx1, final, MD5_SIZE);
        else
            px_md_update(ctx1, (const uint8 *) pw, strlen(pw));
        px_md_finish(ctx1, final);
    }

    p = passwd + strlen(passwd);

    l = (final[0] << 16) | (final[6] << 8) | final[12];
    _crypt_to64(p, l, 4);
    p += 4;
    l = (final[1] << 16) | (final[7] << 8) | final[13];
    _crypt_to64(p, l, 4);
    p += 4;
    l = (final[2] << 16) | (final[8] << 8) | final[14];
    _crypt_to64(p, l, 4);
    p += 4;
    l = (final[3] << 16) | (final[9] << 8) | final[15];
    _crypt_to64(p, l, 4);
    p += 4;
    l = (final[4] << 16) | (final[10] << 8) | final[5];
    _crypt_to64(p, l, 4);
    p += 4;
    l = final[11];
    _crypt_to64(p, l, 2);
    p += 2;
    *p = '\0';

    /* Don't leave anything around in vm they could use. */
    px_memset(final, 0, sizeof final);

    px_md_free(ctx1);
    px_md_free(ctx);

    return passwd;
}
